Genetically enhanced “mighty mice” that were part of a health experiment on the International Space Station held onto their muscle during a monthlong stay at the International Space Station, returning to Earth with ripped bodybuilder physiques, scientists reported on Monday.

According to a recently published study, an experimental drug has dramatically increased the muscle and bone mass in mice that spent over a month on the ISS. The results could be used to develop therapies that might help astronauts mitigate the muscle and bone loss they experience during long-term spaceflight.

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One of the major obstacles to long-term space missions is the threat of severe bone loss in astronauts. In the microgravity environment of space, astronauts lose on average 1% to 2% of their bone mineral density every month.

The new findings hold promise for preventing muscle and bone loss not only for astronauts but also to people who are confined to bed or need wheelchairs.

It was a research team led by Dr. Se-Jin Lee of the Jackson Laboratory in Connecticut which had sent 40 young female black mice to the space station in December, launching aboard a SpaceX rocket.

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In a recent paper published in the Proceedings of the National Academy of Sciences, Lee said the 24 regular untreated mice lost considerable muscle and bone mass in weightlessness as expected — up to 18%. However, the mutant mice which were launched with double the muscles maintained their bulk.

The treatment involves blocking a pair of proteins that typically limit muscle mass.